Measurements of the auroral luminosity at 3914 ¿ and 5577 ¿ made by the auroral scanning photometer on board the Isis 2 polar-orbiting spacecraft are utilized to define the limits of auroral particle precipitation and the locations of discrete auroral arcs above a meridian chain of magnetometers. Locations of the auroral electrojets in this meridian, deduced from the magnetometer data, are related to the features of the optical aurora. Of 56 passes of the satellite in the evening sector during January 1972, 19 passes were found in which the electrojet was sufficiently stable that comparisons are valid. It is found that the electrojet is contained within, and may be narrower than, the latitude range of auroral precipitation. The basic conductivity channel is produced by diffuse auroral precipitation, which is a persistent feature of the evening auroral oval, since electrojets are observed without embedded discrete arcs. Discrete arcs are, at times, observed poleward of the electrojets. These arcs are deficient in current requiring either a depression or a reversal of the ionospheric electric field in their vicinity. Discrete arcs within the electrojet may produce enhanced conductivity in their vicinity, but this does not necessarily lead to enhanced current densities. It is concluded that the poleward edge of the electrojet is governed by the morphology of the electric field, while decreasing precipitation is important at the equatorward edge.